Method for preventing coking in fluidized bed reactor for cracking heavy hydrocarbon oil

Abstract

In a reactor for cracking heavy hydrocarbon oil through a fluidized bed of particles of natural ores, coke-like materials are deposited on a top of the reactor or pipe inside surfaces of a transfer line from the reactor to a scrubber. To effectively scour out the deposited coke-like materials, particles of natural ores having a mean diameter of a few hundred μm is made to be contained in an effluent gas from the top of reactor, passing through the transfer line at a concentration of 1 to 40 g/m 3 . The particles of natural ores have a good effect of scouring out the deposited coke-like materials and can keep the transfer line efficiently clean even with a small amount of the particles of natural ores, decreasing a pressure drop in the transfer line.

What is claimed is: 
     
       1. In a method for cracking heavy hydrocarbon oil by means of an apparatus comprising a reactor column of fluidized bed type for cracking heavy hydrocarbon oil in a fluidized bed of fluidization particles formed by a fluidization gas passing upwardly therethrough, a regenerator column for burning the fluidization particles with coke deposited during the fluidization in the reactor column, thereby removing the coke from the fluidization particles and recycling the thus regenerated fluidization particles to the reactor column, and a transfer line for transferring a cracked effluent gas of the heavy hydrocarbon oil from the top of the reactor column to a successive treatment, a method for preventing coking in the reactor column of fluidized bed type which comprises using natural ores as the fluidization particles and entraining the fluidization particles in the effluent gas to be passed through the top of the reactor column through the transfer line at a rate of 1-40 g/m 3  of the effluent gas, while circulating a host of the fluidization particles between the reactor column and the regenerator column. 
     
     
       2. A method according to claim 1, wherein the particles of natural ores are selected from those of nickel ores, iron ores, copper ores, and limestone having a true density of 3 to 5 g/m 3 . 
     
     
       3. A method according to claim 2, wherein the particles have an average diameter of 60 to 500 μm. 
     
     
       4. A method according to claim 1, providing mixing means of the fluidization particles, comprised of a particle vessel and a control gas supply inlet provided below and communicated with the particle vessel, and wherein the fluidization particles to be entrained are controlled to said rate by controlling the gas. 
     
     
       5. A method according to claim 2, wherein the particles of natural ores are treated by heating at about 800° to 1,300° C. 
     
     
       6. A method according to claim 1, wherein the effluent gas from the top of reactor through the transfer line had a fluid velocity of 20 to 100 m/sec. 
     
     
       7. A method according to claim 1, wherein an insert for inhibiting passage of the fluidization particles towards the transfer line, accompanying the effluent gas, is provided in an upper space part of the reactor column, a lift gas supply line is provided through the insert, and the fluidization particles are entrained in the effluent gas at said rate by a mixing means of the fluidization particles provided in the lift gas supply line. 
     
     
       8. A method according to claim 1, wherein a pressure drop of the effluent gas through the transfer line is detected, and an amount of the fluidization particles blown up to the top of the reactor is controlled according to the detected pressure drop. 
     
     
       9. In a method for cracking heavy hydrocarbon oil by means of an apparatus comprising a reactor column of fluidized bed type for cracking heavy hydrocarbon oil in a fluidized bed of fluidization particles formed by a fluidization gas passing upwardly therethrough, a regenerator column for burning the fluidization particles with coke deposited during the fluidization in the reactor column, thereby removing the coke from the fluidization particles and recycling the thus regenerated fluidization particles to the reactor column, a cyclone provided at the upper space part of the reactor column for separating the fluidization particles accompanying a cracked effluent gas of the heavy hydrocarbon oil, and a transfer line for transferring the effluent gas from the top of the reactor column to a successive treatment, a method for preventing coking in the reactor column of fluidized bed type which comprises using natural ores as the fluidization particles, blowing the fluidization particles toward an inlet of the cyclone at the upper space part of the reactor column, controlling a recovery efficiency of the cyclone, thereby entraining the fluidization particles in the effluent gas to be passed through the top of the reactor column and the transfer line at a rate of 1-40 g/m 3  of the effluent gas, while circulating a host of the fluidization particles between the reactor column and the regenerator column. 
     
     
       10. A method according to claim 9, including supplying an aeration gas to a dip leg of the cyclone, thereby changing the separation efficiency of the cyclone. 
     
     
       11. A method according to claim 9, wherein the fluidization particles of natural ores are selected from those of nickel ores, iron ores, copper ores, and limestone having a true density of 3 to 5 g/m 3 . 
     
     
       12. A method according to claim 11, wherein the particles have a mean diameter of 60 to 500 μm. 
     
     
       13. A method according to claim 9, wherein a pressure drop of the effluent gas at the outlet of the cyclone is detected, an amount of the fluidization particles blown up to the inlet of the cyclone is controlled according to the detected pressure drop, a pressure drop of the effluent gas in the transfer line is detected, and a recovery efficiency of the cyclone is controlled according to the detected pressure drop in the transfer line. 
     
     
       14. A method according to claim 11, wherein the particles of natural ores are treated by heating at about 800° to 1,300° C. 
     
     
       15. A method according to claim 9, wherein the effluent gas from the top of reactor through the transfer line has a fluid velocity of 20 to 100 m/sec. 
     
     
       16. A method according to claim 9, removing coke deposited on a cyclone wall by providing a particle lift line with a mixing means of the fluidization particles provided near an inlet part of the cyclone. 
     
     
       17. A method according to claim 16, providing mixing means of the fluidization particles, comprised of a particle vessel and a control gas supply inlet provided below and communicated with the particle vessel, and wherein the fluidization particles are controlled to said rate by controlling the control gas.